Are flush draws really such a massive part of his range (which is A's and flush draws? AFAIK) that we really can bet the river profitably? What's our sizing?
i hate checking the turn and betting river as villian will give you zero credit with weak marginal hands, add to that the pot will be smaller allowing him to hero more often
also he can bet any of his many possible draws that he would of folded to a 3 barrel, thus making you fold